Abstract: A hydraulic power supply unit has a fluid reservoir and a motor-driven pump which delivers fluid under pressure to a hydraulic system through a check valve in a fluid supply line. A hydraulic pressure accumulator downstream of the check valve helps maintain the system under a predetermined pressure. An accumulator pressure release valve automatically relieves the accumulator and thus the connected system of hydraulic pressure when the pump is inactive. The valve has a valve body with a pilot port connected to the discharge side of the pump upstream of the check valve, an accumulator port in communication with the accumulator and a return port in communication with the reservoir. Internal passages within the valve body interconnect the pilot, accumulator and return ports. A movable valve member within the valve body moves to a closed position when the pump operates to block flow from the accumulator port to the return port, thereby pressurizing the accumulator and the system.